DESCRIPTION (Adapted from applicant s description): The investigators propose that Nitric Oxide (NO), which is elevated in pregnancy, regulates the biosynthesis of fibril-forming collagen of the vasculature at both the pre-and post translational level. The first hypothesis: Nitric Oxide (NO) increases type III collagen synthesis over type I collagen synthesis in vascular smooth muscle cell cultures and in isolated rat mesenteric arteries is based upon the preliminary data showing that NO specifically up regulates mRNA abundance for COL3A1, the gene for type III collagen. In aim 1 the investigator will examine a) whether increased COL3A1 mRNA levels result in higher secretion of the corresponding protein in cell cultures and isolated rat mesenteric resistance arteries using biochemical methods and b) which transcriptional and posttranscriptional mechanisms regulate the COL3A1 mRNA increase by methods of molecular biology. Higher incorporation of type III collagen into the perivascular matrix of resistance arteries could increase compliance and elasticity, as has been shown for numerous connective tissues. The second hypothesis: Nitric Oxide decreases overall collagen synthesis in vascular smooth muscle cell cultures and in isolated rat mesenteric arteries by inhibiting propyl-4 hydroxylase is based upon studies in chondrocyte cultures showing that Nitric Oxide inhibits this posttranslational enzyme of collagen biosynthesis. In Aim 2 the effect of NO on enzymatic activity of prolyl-4 hydroxylase in vascular smooth muscle cell cultures and in isolated rat mesenteric arteries will be examined biochemically.